One more thing you can try (this makes little sense, but it works for me!):

Boot Knoppix. When you get to the boot prompt, do an expert boot. Answer n to the half dozen questions you are asked (specifically, do not let it do the autoprobe in the first question). See if you network connection works now after Knoppix finishes booting.

If all else fails, see http://www.knoppix.net/forum/viewtopic.php?t=2164